Neo-Darwinism's Unsolved Problem of the Origin of Morphological Novelty

Fellows of the Center for Science & Culture
Discovery Institute
October 11, 2004

Part I: One Long Bluff

Discovery Institute Senior Fellow Stephen C. Meyer's recent article, "The Origin of Biological Information and the Higher Taxonomic Categories," published in Proceedings of the Biological Society of Washington (PBSW) 1, has provoked a storm of criticism from Darwinists because it develops a case for the theory of intelligent design (ID) in a peer-reviewed science journal. So far, however, the only critique of the article's content has been an Internet response titled "Meyer's Hopeless Monster," written by three staff members of the militantly pro-Darwin National Center for Science Education -- Alan Gishlick, Nicholas Matzke, and Wesley R. Elsberry (hereafter GME). 2

Since Nature gave unusual prominence to GME's Internet critique in a news article about the publication of Meyer's article 3, we have decided to provide a detailed response to their critique in a series of installments to be posted here over the next few weeks.

Our first installment, "One Long Bluff," was posted October 5, 2004. It summarized the arguments in Meyer's article in a list of eight propositions, and it summarized GME's critique in a list of six points.

Meyer argues that the origin of body plans (and other morphological novelties) during the history of life is increasingly recognized as a fundamental and unsolved problem in theoretical and evolutionary biology. He also argues that there is a good reason for this. In particular, he notes that neo-Darwinism attempts to account for the origin of novel form as the result natural selection acting solely on genetic variations of different kinds. Yet the construction of novel body plans depends upon new sources of epigenetic (as opposed to just genetic) information, and genes alone do not generate this higher-level information and structure.

These two claims—namely, that biologists now recognize the problem of novel form and that neo-Darwinism does not solve it—constitute two parts of the argument that Meyer developed in his PBSW piece. For those keeping track, these two claims constitute the first and sixth (of eight) propositions in Meyer's argument, as summarized in our first response to GME. Since these two propositions are obviously closely related, we will address them together here.

Do GME rebut these two parts of Meyer's argument?

We don't think so.

GME claim that current evolutionary theory does account for the origin of morphological novelty. They also fault Meyer for not citing scientific papers that allegedly establish this claim.

As we show here, however, it is actually GME who fail to cite numerous scientific papers that support Meyer's argument, and the papers they do cite fail to solve the problem Meyer addresses. Specifically, we will show three things:

(I) GME ignore the large body of peer-reviewed biological literature supporting Meyer's contention that the origin of morphological novelty is a fundamental and unsolved problem for evolutionary theory.

(II) The literature that GME do cite to show that this problem has been solved is obsolete or irrelevant, or it actually supports Meyer's case.

(III) GME fail to address, let alone rebut, Meyer's detailed analysis of why neo-Darwinism, self-organization theory and structuralism do not account for the origin of new forms and body plans.

Let's look at these three points in detail.

(I) The unsolved problem.

GME begin their summary of Meyer's article by stating that it "predictably follows the same pattern that has characterized 'intelligent design' since its inception: deny the sufficiency of evolutionary processes to account for life's history and diversity, then assert that an 'intelligent designer' provides a better explanation." GME then defend the sufficiency of evolutionary theory by citing scientific papers that allegedly solve the problems with neo-Darwinism that Meyer discusses and by ignoring an extensive body of biological literature that support Meyer's critique of same. A casual reader might, therefore, think that Meyer simply invented these problem.

But this is not the case.

Indeed, when addressing the general public, evolutionary biologists often write as though Charles Darwin's theory of natural selection long ago solved the twin problems of the origin of body plans (the disparate anatomical architectures of animals) and the origin of morphological novelties (complex structures such as limbs, eyes, or feathers). "The theory of evolution by natural selection," wrote Ernst Mayr in 2000, "explains the adaptedness and diversity of the world solely materialistically.... Every aspect of the 'wonderful design' so admired by the natural theologians could be explained by natural selection." 4

More recently, Francisco Ayala wrote: "It was Darwin's greatest accomplishment to show that the directive organization of living beings can be explained as the result of a natural process -- natural selection." 5

Judging solely from statements such as these, one might conclude that evolutionary biologists have already solved the problem of the origin of new morphologies and body plans, at least in principle. It would seem that all that remains is to fill in the details.

Behind the curtain of public pronouncements, however, biologists know that this is not the case. Life scientists have long questioned the sufficiency of known evolutionary processes to solve the problem -- and such skepticism continues unabated. In the introduction to his article, Meyer documents this controversy with extensive citations to the current scientific literature.

For example, Meyer cites a recent volume of The Vienna Series in Theoretical Biology in which Gerd B. Muller and Stuart Newman argue that what they call the "origination of organismal form" remains an unsolved problem. 6

Meyer cites more than a dozen other scientific publications in the past ten years in which other biologists have written essentially the same thing.

These citations are merely a reflection of a decades-long debate within the biological science community. For example, evolutionary geneticist Wallace Arthur wrote in 1997 that "current evolutionary theory, based on natural selection and adaptation in present-day lineages is, at the very least, incomplete," hence "the feelings of dissatisfaction that many evolutionary developmental biologists have with neo-Darwinism." 7

Referring specifically to the problem posed by the abrupt appearance of many different animal body plans in the Cambrian explosion, paleontologist Robert Carroll wrote in 2000: "This explosive evolution of phyla with diverse body plans is certainly not explicable by extrapolation from the processes and rates of evolution observed in modern species." 8

More recently, in his 2004 book On the Origin of Phyla, paleontologist James Valentine evaluates various attempts to explain (or explain away) the origin of the body plans that arise in the Cambrian. He concludes that no current hypothesis provides a satisfactory account of the origin of the Cambrian phyla and that the problem of novel body plans remains unsolved—or, as he puts it "the underlying causes remain uncertain." 9

Even Kevin Padian, before he became president of the militantly Darwinist organization in which GME all work as staff members, acknowledged that there is an unsolved problem here. "How do major evolutionary changes get started?" he wrote in 1989. "I would like to see a new evolutionary synthesis that approaches questions of how morphogenesis [the development of form] constructs new features, and how it does so well, so often, and so quickly." 10

GME totally ignore this body of literature, while brazenly criticizing Meyer for omitting "discussion or even citation of vast amounts of directly relevant work available in the scientific literature." Of course -- as GME would be quick to point out -- none of the scientists cited above are proponents of ID. Instead, all of them are optimistic that materialistic evolutionary processes will eventually solve the problem of the origin of new morphologies and body plans, and they propose various hypotheses that they hope will contribute to the solution. But they unanimously acknowledge the problem. Meyer did not invent it; he simply proposed a different solution.

(II) GME's obsolete or irrelevant citations.

GME also claim, contra Meyer, that neo-Darwinism (or some variant of it) can explain the origin of novel forms and structures. They write: "Meyer fails to incorporate any of the work on the origin of morphological novelties in geologically recent cases where evidence is fairly abundant, and Meyer also fails to discuss the crucial role that co-option plays in the origin of novelty. Below is a small sampling of the kinds of papers that Meyer would have had to address in this field in order to even begin to make a case that evolution cannot produce new morphologies." The small sampling includes four journal articles and one book chapter. [11-15] Since GME apparently consider these citations to provide a definitive rebuttal of Meyer's assertion that neo-Darwinian theory fails to explain the origin of morphological novelties, they are worth looking at in some detail. Let's start with the book chapter, which GME suggest solved the problem over forty years ago.

(a) Ernst Mayr, "The Emergence of Evolutionary Novelties." (1960). 11

According to GME, "Mayr wrote this in 1960, at the sprightly age of 56, but it applies rather well to discoveries about the origin of new genes and new morphological structures made in the last few decades. Most new genes and new structures are derived by change-of-function from old genes and old structures, often after duplication."

Mayr's chapter asks the question, "What controls the emergence of evolutionary novelties?" And Mayr's answer is: "The emergence of new structures is normally due to the acquisition of a new function by an existing structure. In both cases the resulting 'new' structure is merely a modification of a preceding structure. The selection pressure in favor of the structural modification is greatly increased by a shift into a new ecological niche, by the acquisition of a new habit, or by both. A shift in function exposes the fully formed 'pre-adapted' structure to the new selection pressure. This, in most cases, explains how an incipient structure could be favored by natural selection before reaching a size and elaboration where it would be advantageous in a new role." (pp. 377-378)

So Mayr argues that new structures emerge when natural selection modifies an existing structure for a new function. But natural selection operates only when three conditions are met: first, there must be variations in some trait; second, those variations must affect how many offspring the organism produces (i.e., its fitness); and third, those variations must be passed on to the offspring (i.e., they must be heritable).16

Mayr provides no evidence that these three conditions are met in any of the cases he describes. For example, he invokes change-of-function and natural selection to explain in detail how lungs evolved in fishes: "As the outer skin became increasingly unsuitable for gas exchange (partly owing to the development of dermal armor) and, even more importantly, as the gills became temporarily rather useless in oxygen-poor stagnant swamps during Devonian drought periods, active air uptake by 'air-swallowing' became at times the most important source of oxygen. At this stage, any enlargement of the surface of the inner throat or esophagus, any formation of diverticles, etc., was favored by natural selection." (p. 366)

How Mayr knows what happened in Devonian swamps is a question only he can answer. At any rate, he provides no evidence for heritable variations capable of producing the traits he describes. As Meyer notes in his essay, building a new body plan or a major new morphological structure (such as a lung) would require more than minor genetic variations that occur late in development. At the very least such morphological innovations would require beneficial mutations occurring during early development. Yet beneficial mutations affecting early development have never been observed. Mayr's 44 year-old paper does not address, and (in fairness) could not have even appreciated, this problem.

Instead, what Mayr proposed was an evolutionary "mechanism" of such untestable generality that it brings to mind the Monty Python skit, "How to Do It." (Would you like to know how to play the flute? It's simple. Just blow into the mouthpiece and move your fingers up and down on the holes. That's how to do it -- now you're playing the flute!) Would you like to know how novel structures arise during evolution? From existing structures, of course, via new selection pressures.

This isn't empirical science. This is story-telling.

GME seem to think that Mayr's story-telling has solved what is arguably the central problem of evolution. Leading evolutionary biologists, however, seem not to have heard the news. Scientists do not work on problems that others have already solved. As current scientific literature and professional meetings attest, however, evolutionary biologists today continue to try to solve the problem of the origin of morphological novelty. Mayr's 1960 book chapter, which provides nothing more than neo-Darwinian generalities and untestable just-so stories, is obsolete.

Let's turn to the other four citations provided by GME, starting with the longest.

(b) Richard O. Prum and Alan H. Brush, "The Evolutionary Origin and Diversification of Feathers." (2002). 12

Feathers are remarkable and complex structures, whose origin and diversification, Prum and Brush argue, have been "intractable questions in evolutionary biology for more than a century." (p. 291) The puzzle of feathers is unsolved, they argue, because of "conceptual problems faced by macroevolutionary biology." (p. 262) These problems include the following:

* Neo-Darwinism (their term) tries to dissolve all morphological novelties into a microevolutionary continuum from some earlier structure. But "genuine evolutionary novelties are distinct from simple microevolutionary changes in that they are qualitatively or categorically different from any antecedent... structure." (p. 265) Because neo-Darwinism miscasts the problem, "few of [its] theories have adequately appreciated the many novel aspects of feather morphology and feather development, and none have formulated adequately detailed hypotheses about the origin and evolution of these morphological and developmental novelties." (p. 265) In other words, according to Prum and Brush, neo-Darwinism has not explained the origin of feathers, a significant morphological novelty.

* "Explicit attempts to reconstruct the evolutionary history of feathers based on natural selection for specific functions have failed to identify an unequivocal, plesiomorphic [ancestral] function of feathers or to accurately predict a transition series of ancestral feather morphologies." (p. 285) This shortcoming has its roots in neo-Darwinism itself: "This failure reveals an inherent weakness of neo-Darwinian attempts to synthesize micro and macroevolution." (p. 289) The origin of feathers cannot be understood by invoking "change-of-function" -- the principal route GME propose for the origin of novelty. For Prum and Brush, change-of-function is an inherently weak approach: "The conceptual basis of functional theories of the origin is weak because these theories rest upon hypotheses about the function of an ancestral structure whose morphology is unknown." (p. 267) Clearly, Prum and Brush do not think that the origin of feathers can be explained by change-of-function. Yet, GME claim that change of function by co-option solves the problems with neo-Darwinism that Meyer described in his essay.

One has to wonder, therefore, why GME cited the article against Meyer. Did they even read it?

Of course, Prum and Brush do go on to assert that natural selection was responsible for the origin of feathers. But they offer no evidence in support of this assertion, only a sketch of the kind of events that "must have" happened in order for feathers to have arisen.

To build feathers where none existed before, Prum and Brush contend, the processes of epidermal development must [emphasis added] first be extensively modified. Developmentally, feathers are characterized by a suite of novel features (e.g., formation of a tubular follicle, helical growth patterns, barbs and barbules), where "derived" or "advanced" features actually arise earlier in avian development than supposedly more primitive features. The authors argue that only after considerable modification of developmental processes could a structure have evolved that might have been used for flight: "Only the most derived and complex feather morphology could yield a feather with advanced aerodynamic function." (p. 286) In other words, primitive feathers could not have been naturally selected for flight.

As we saw above, natural selection operates only when there are fitness differences. If primitive feather morphologies were not selected for flight, what fitness differences did they provide? Prum and Brush decline to speculate, because any number of possibilities exist, and we may never know. "In fact," they write, "the possibility of gathering morphological or behavioral information from fossil representatives of the actual lineages in which this event occurred is essentially impossible, and we can rationally abandon hope of identifying a singular functional explanation." (pp. 286-7)

Nevertheless, Prum and Brush are convinced that natural selection was involved in the origin of feathers: "Whatever it was, the initial functional advantage of the earliest feathers constituted natural selection for an emergent appendage that then fostered the evolution of the feather follicle (Stage I). Although the original functional advantage of the first feathers remains a mystery, the ultimate explanation for the origin of the feather must have [emphasis added] involved selection for epidermal appendages that emerged from the skin." (p. 287)

Prum and Brush conclude: "The hypothesis that feathers evolved by natural selection for flight is falsified, but numerous other proposed initial functions of feathers remain plausible. More specifically, feathers likely originated by selection for the growth of an integumentary appendage that emerged from the skin." (p. 291)

In other words, Prum and Brush propose another hypothesis for how natural selection might have produced a morphological novelty, but they do not explain how the necessary appendages or structures were built in light of the specific problems with the neo-Darwinian mechanism that Meyer addresses in his essay (see below "(III) GME's failure to address Meyer's analysis"). Indeed, considering, that Prum and Brush themselves admit that "the original functional advantage of the first feathers remains a mystery," their hypothesis hardly rises above the level of Mayr's just-so stories.

So once again, we have GME presenting an untested and probably untestable hypothesis -- a speculation, really -- as though it were evidence. Of course, Prum and Brush are certainly welcome to offer speculative hypotheses. The fact that they have done so, however, does not (contra GME) refute Meyer's claim that the origin of novel form remains an unsolved problem within evolutionary theory.

(c) John R. True and Sean B. Carroll, "Gene Co-option in Physiological and Morphological Evolution." (2002).13


The first two-thirds of this review article presents comparative data on protein multi-functionality, along with various post-hoc scenarios about how that multi-functionality might have evolved. According to the authors, it evolved through "co-option," which "occurs when natural selection finds new uses for existing traits." (p. 53)

Protein multi-functionality is a fascinating phenomenon. Proteins known as crystallins, for instance, function as structural elements in the lenses of animal eyes, in protecting cells from heat shock, and as metabolic enzymes. The protein Distal-less functions in limb development in animals as diverse as mammals and insects, but also in the development of eyespots on butterfly wings. Discoveries from cell and developmental biology over the past two decades have revealed many such cases of protein multi-functionality, in a wide array of species.

True and Carroll argue that these cases indicate "that current diversity among phyla of modern organisms has extensively involved new combinations and modifications of pre-existing molecular characters. The acquisition of new roles by ancestral characters or new characters from old ones is known as co-option. Changes at the level of genes, either in regulation or function, underlie co-option." (p. 54)

So True and Carroll propose to explain the origin of multi-functionality by invoking changes in gene regulation or function. In the last third of their article they go looking for evidence that this mechanism actually works. When it comes to morphological novelties, however, the evidence isn't there. Assuming gene transposition and duplication, True and Carroll conclude: "The mechanisms by which duplication and transposition bring about co-option of novel gene functions have thus far been hidden from view because functionally important polymorphisms [i.e., variations] involving these events are difficult to identify. The next phase of evolutionary developmental biology research must address this paradox by investigating the levels, causes, and consequences of microevolutionary variation in developmental systems." (p. 74)

In other words, the variations upon which natural selection would have to work remain elusive, just as they were for Mayr and for Prum and Brush, and the mechanism of co-option remains hypothetical.

This doesn't stop True and Carroll from treating it as a reality. After 19 pages of "similarity implies co-option" speculation, True and Carroll conclude that "we have seen that gene co-option has been a widespread and important process for both ancient and recent evolution." (p. 69)

Hold the phone. "We have seen?" We have seen nothing of the sort. What we have here is like something out of Alice in Wonderland: Verdict first, evidence later.

Imagine a prosecutor who begins his courtroom remarks with the statement, "Given that we know the defendant committed the crime..." -- then shows a body to the jury but moves directly to the penalty phase of the trial without ever presenting any evidence that the defendant was the cause of the victim's death.

If there were actual evidence showing that a neo-Darwinian mechanism was the cause of protein multi-functionality, one would expect to find it in True and Carroll's article. Once again, however, what we have is hypothesis masquerading as evidence.

Co-option may or may not occur. Unless scientists are careful to separate evidence from speculation, however, they may assume what needs to be demonstrated and find themselves believing in evolutionary "mechanisms" whose empirical support is illusory. Contrary to the claim of GME, the article by True and Carroll does not refute Meyer's argument. If anything, True and Carroll's admission about the lack of observational evidence for mechanisms of co-option actually supports it.

(d) Maria D. Ganfornina and Diego Sánchez, "Generation of evolutionary novelty by functional shift." (1999).14

The first half of this review article juggles definitions, verbal distinctions, and speculative evolutionary scenarios. The authors define the terms "functional shift," "co-optation," "exaptation," and "co-option," but provide no experimental or observational evidence for the operation of any of these hypothetical mechanisms.

The reason the authors provide no experimental evidence becomes obvious in the second half of the article. There, actual genes and proteins make their appearance, but only in the post hoc comparative fashion discussed above in our analysis of the article by True and Carroll. Ganfornina and Sánchez observe that proteins may be multi-functional, but (like True and Carroll) they move directly from this speculation to the conclusion that those proteins originated through evolutionary co-option.

But what evidence do they provide that co-option actually happens? None. This, they write, is a topic for future research: "First, we need to convincingly detect co-option and duplication events along the history of genes, developmental modules, or morphologic structures. In general, it would be very difficult to catch evolutionary events of co-option or gene duplications in current populations to experimentally test the hypotheses proposed here... Second, we need to search for the mechanisms responsible for the evolutionary processes of co-option and duplication. Although much is known about the former, almost nothing is known about co-option mechanisms." (p. 438)

Ganfornina and Sánchez argue that any approach to co-option "by definition, has to be hypothetico-deductive." (p. 438) In other words, evolution by natural causes is assumed to be true, and inferences are then drawn from that assumption. As we noted in the first installment of our response to GME, it is philosophically legitimate to presuppose a theory as a guide to research, but this is not the same as providing evidence for the theory. When the truth or falsity of the theory itself is the issue, as it is here, working out its logical implications is a largely irrelevant exercise.

In short, this article, like the three before it, does nothing to rebut Meyer's arguments, if anything, it reinforces Meyer's contention that the problem of the origin of novel form remains unsolved

(e) Olle Pellmyr and Harald W. Krenn, "Origin of a complex key innovation in an obligate insect-plant mutualism." (2002).15

Yucca moths and yucca plants jointly constitute one of the most remarkable mutualisms in biology. Yucca moths exclusively pollinate yucca plants, which in turn provide food in their seeds for yucca moth larvae. Female yucca moths possess unique mouthparts — tentacles — which they use to manipulate and deposit yucca pollen grains.

The origin of these tentacles is unknown. Pellmyr and Krenn note that they "are a rare example of a complex key innovation that emerged in one clade [i.e., branch of the evolutionary tree] without any homologous structure in related taxa." (p. 5500) The tentacles, however, share some anatomical features with nearby mouthparts, the galeae, which unite to form a long coiling proboscis in moths. "The simplest explanation for the shared specializations between the tentacle and galea," argue Pellmyr and Krenn, "is that a shared developmental pathway is involved." (p. 5501) Perhaps, then, the distinctive tentacles of yucca moths evolved by "protracted expression" of a transcription factor at a "novel site" that created the unique tentacles of female yucca moths.

Of the five papers cited by GME, this study by Pellmyr and Krenn is by far the most narrowly focused, speculating about the origin of a single, fairly minor anatomical novelty — and thus in an important sense this paper is also the most reasonable. We can imagine follow-up studies that would genetically dissect the developmental pathways of yucca moth tentacles, to see if Pellmyr and Krenn's hypothesis is at least consistent with the evidence.

But (judging from this article) those studies have not been done. "[I]t should be important," note Pellmyr and Krenn, "to test the explicit predictions about patterns of gene expression that derive from this hypothesis." (p. 5502) Yes, indeed.

But the origin of novel anatomical structures in insects, even relatively minor structures such as yucca moth tentacles, has never been observed. It would take an experiment worthy of a Nobel Prize to demonstrate the evolutionary pathway from mutations to novel morphologies, in insects or any other animal group. This study, which is strictly comparative, does not show that. Nor, frankly, do we ever expect to observe such a thing. Pellmyr and Krenn have suggested a possible evolutionary mechanism whose genetic and developmental components are entirely unknown (if in fact they exist at all). Therefore, this publication, like the other four, falls far short of rebutting Meyer's arguments.

(III) GME's failure to address Meyer's analysis.

Meyer's critique of neo-Darwinism addresses a much deeper question than most of the articles that GME cite against him. Whereas these papers offer stories or scenarios of varying plausibility, Meyer asks some fundamental questions about how novel structures, and especially body plans (unique arrangements of body parts), could arise by mutation and selection. Meyer wants to know how new form is constructed and whether the neo-Darwinian mechanism (or other proposed causes of evolution) can explain the origin of such form given what we know about, for example, developmental biology. Meyer criticizes neo-Darwinism for its inability to account for the origin of new morphologies and body plans, on two grounds: (a) neo-Darwinism relies on beneficial genetic mutations affecting early development, yet such mutations have never been observed; and (b) DNA does not wholly determine morphological development, yet according to neo-Darwinism selection acts upon exclusively genetic mutations as the ultimate source of new form.

Meyer also criticizes the principal materialistic alternatives to neo-Darwinism, self-organization theory and structuralism, because (c) although they may explain redundant patterns they cannot explain the origin of information-rich structures such as DNA. Let's look at each of these points, and at how GME address them.

(a) According to neo-Darwinian theory, genetic mutations provide the raw materials on which natural selection acts to produce evolutionary novelties. Since animal body plans are determined very early in development, mutations that could potentially produce new body plans must affect early embryos. Yet mutations that have been observed to act early in development either have no effect or they are harmful -- and the earlier and more extensive their effects, the more harmful they tend to be. This is not surprising, since disrupting early development would be expected to disrupt all the highly integrated processes that follow. Meyer gives specific examples and documents his assertions with references to the relevant scientific literature. He concludes that developmental biology has uncovered "a profound difficulty for neo-Darwinism." The difficulty is that "there is no evidence from developmental genetics that the kind of variations required by neo-Darwinism -- namely, favorable body plan mutations -- ever occur."

(b) Developmental biologists have long been aware that DNA does not wholly determine morphological form. Although DNA helps to direct protein synthesis, DNA alone does not determine how individual proteins assemble themselves into larger systems of proteins; still less does it solely determine how cell types, tissue types, and organs arrange themselves into body plans. There is considerable evidence that other factors, including the three-dimensional structure and organization of the cell membrane and cytoskeleton, play important roles in determining morphology as the embryo develops. Having already argued that the neo-Darwinian mechanisms of mutation and selection are incapable of producing the information in DNA, Meyer also argues that neo-Darwinism does not account for the preexisting three-dimensional patterns and organization that are necessary to produce organismal form.

How do GME react to these two points? They misconstrue Meyer's argument, ignore what he says, and criticize him for something he didn't say.

In the first place, according to GME, "Meyer implies that the lack of specificity of development in genes is a surprising problem for evolution, yet it is well known and it is widely recognized that development is coordinated by epigenetic interactions of various cell lineages. Meyer treats this fact as if it were some mysterious phenomenon requiring a designer to input information." Actually, it is true that genes are remarkably non-specific in development. The ubiquity of similar Hox genes in animals as radically different as worms, sea urchins, flies and mammals is a case in point. Other biologists have argued that this lack of specificity poses a problem for neo-Darwinian evolution, but this is not Meyer's argument. Meyer's argument is that there is no evidence for the sorts of beneficial morphological mutations required by neo-Darwinian theory and good theoretical reasons for doubting that they will occur. GME utterly fail to address this point.

Secondly, GME's insinuation that Meyer overlooks epigenetic interactions is so blatantly false that one wonders whether they even read his article -- or, if they did, why they misunderstand or misrepresent his argument. In fact, Meyer devotes several pages to discussing epigenetic interactions in animal development. Far from treating them as "some mysterious phenomenon," he shows how our present knowledge of cytoskeletal dynamics and membrane patterns challenges the neo-Darwinian emphasis on genetic programs as the basis of morphogenesis.

GME fault Meyer for failing to mention a 1987 book by Leo Buss [17], which, they claim, "extensively documented" how animals evolved "by competition between variant cell lineages." According to GME, Buss showed that the evolution of animal body plans "involved an exchange between selection at the level of the individual and at the level of the cell lineage, which was sorted through developmental interactions." The implication is that Buss settled the issue seventeen years ago, and Meyer is negligent for failing to acknowledge the fact.

Actually, however, Buss's book is an essay in evolutionary theory. He wrote: "I advocate a modification of the synthetic theory of evolution [i.e., neo-Darwinism] which I believe holds the potential for specific evolutionary predictions regarding the natural history of development, cell structure and genomic organization. At the heart of my arguments is the simple observation that the history of life is a history of the elaboration of new self-replicating entities by the self-replicating entities within them." In effect, Buss is here simply re-stating Darwin's concept of descent with modification. Buss goes on to propose his "fundamental thesis," namely that "the evolution of individuality becomes comprehensible not by the study of ancient constraint, nor by the study of selection upon individuals, nor even by the study of selection on cell lineages, but only through the study of their interactions." In other words, except for adding cell lineages to the mix, Buss's proposal is mainly a re-statement of classical Darwinian theory. In any case, he does not provide any actual evidence that morphology can be heritably modified by "interactions among cell lineages." That is, he fails to show that necessary epigenetic sources of form (or information) are variable in a way that is heritable and would provide the basis for beneficial macro-evolutionary change.

Several things can be said about GME's smug reliance on Buss's book. First, since it was a theoretical work, their claim that the book "extensively documented" how animals evolved "by competition between variant cell lineages" is false. Second, the continuing controversy among evolutionary biologists over the origin of animal body plans shows that Buss did not solve the problem. Indeed, GME's citation of the book is best described as an example of "literature bluffing" -- the science-stopping diversionary tactic we described in the first installment of our response to GME.

(c) Meyer argues that two of the principal materialistic alternatives to neo-Darwinism -- self-organization theory and structuralism -- also fail to solve the problem of the origin of morphological novelties and animal body plans. According to self-organization theory, biological forms are emergent patterns that self-organize via the laws of nature. Yet the model systems used to illustrate self-organization theory presuppose rather than explain the preexisting information on which they depend. Furthermore, since the models are not constrained by functional considerations they are not analogous to biological systems. According to structuralism, biological forms arise from the continuous ahistorical operation of fundamental laws that organize or inform matter. Although the latter can account for redundant patterns, however, they cannot account for the origin of aperiodic information-rich structures such as DNA or the spatial organization of an egg. Like self-organization theory, structuralism presupposes rather than explains the origin of complex specified information.

How do GME react to this argument? They ignore Meyer's argument, present a simple-minded illustration as though it settles the issue, and make the preposterous claim that because of the illustration biologists already understand developmental programs.

According to GME, "just as the ordered structure of convection cells in [a] boiling pot of water is not a mystery to physicists even though it is not specified by the shapes of the component water molecules, neither are developmental programs to biologists. The convection cells are an emergent property of the interactions of the water molecules, just as the growth of organismal form is an emergent property of the interactions of cell lineages." Not a word about the fundamental difference between redundant patterns and aperiodic information-rich structures. Not a word about the origin of the form-producing information that is necessary even to make convection cells possible. And not a word about the many unknown details of cell interactions involved in determining whether an organism will be a worm, a sea urchin, a fly or a mammal. Only the faddish term "emergent property," which lacks explanatory content altogether.

If GME really believe that developmental programs are no more mysterious to biologists than convection cells are to physicists, they should get out more -- maybe go to a seminar or two and think about what's being said, or actually read and critically analyze some developmental biology journal articles.

Simply bluffing will not do.

NOTES

1 Stephen C. Meyer, "The Origin of Biological Information and the Higher Taxonomic Categories," Proceedings of the Biological Society of Washington 117 (2004): 213-239.

2 Alan Gishlick, Nick Matzke, and Wesley R. Elsberry, "Meyer's Hopeless Monster," The Panda's Thumb (posted August 24, 2004), http://www.pandasthumb.org/pt-archives/000430.html

3 Jim Giles, "Peer-reviewed paper defends theory of intelligent design," Nature 431 (2004): 114.

4 Ernst Mayr, "Darwin's Influence on Modern Thought" Scientific American (July, 2000): 78-83.

5 Francisco J. Ayala, "Design Without Designer: Darwin's Greatest Discovery," pp. 55-80 in Michael Ruse and William A. Dembski (eds.), Debating Design: From Darwin to DNA (Cambridge: Cambridge University Press, 2004).

6 Gerd B. Müller and Stuart A. Newman (eds.), Origination of Organismal Form: Beyond the Gene in Developmental and Evolutionary Biology (Cambridge, MA: The MIT Press, 2003).

7 Wallace Arthur, The Origin of Animal Body Plans: A Study in Evolutionary Developmental Biology (Cambridge: Cambridge University Press, 1997), pp. 3-10.

8 Robert L. Carroll, "Towards a new evolutionary synthesis," Trends in Ecology and Evolution 15 (2000): 27-32. See also: Sean B. Carroll, "The big picture," Nature 409(2001): 669.

9 James Valentine, On the Origin of the Phyla (Chicago: University of Chicago Press, 2004), pp. 189-195.

10 Kevin Padian, "The Whole Real Guts of Evolution?" Paleobiology 15 (1989): 73-78.

11 Ernst Mayr, "The Emergence of Evolutionary Novelties," pp. 349-380 in Sol Tax (ed.), Evolution After Darwin: Volume 1: The Evolution of Life: Its Origin, History, and Future (Chicago: The University of Chicago Press, 1960).

12 Richard O. Prum and Alan H. Brush, "The evolutionary origin and diversification of feathers," Quarterly Review of Biology 77 (2002): 261-295.

13 John R. True and Sean B. Carroll, "Gene Co-Option in Physiological and Morphological Evolution," Annual Review of Cell and Developmental Biology 18 (2002): 53-80.

14 Maria D. Ganfornina and Diego Sánchez, "Generation of evolutionary novelty by functional shift," Bioessays 21(1999): 432-9.

15 Olle Pellmyr and Harald W. Krenn, "Origin of a complex key innovation in an obligate insect-plant mutualism," Proceedings of the National Academy of Sciences USA 99 (2002): 5498-5502.

16 Endler, John. 1986. Natural Selection in the Wild. Princeton: Princeton University Press.

17 Leo W. Buss, The Evolution of Individuality (Princeton: Princeton University Press, 1987).

Part I: One Long Bluff